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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-10-24 19:19:33 +0000
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-10-30 17:11:10 -0300
commit5e46749c64d51f50f8511ed99c1266d7c13e182b (patch)
treee3fd42d4cb28b3863daff8585588d0c69d27b3cd /NEWS
parent40a36935fff4eac83b9676b04048990ccb3c4754 (diff)
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Use clock_gettime to implement gettimeofday.
Consolidate generic gettimeofday implementation to use clock_gettime. Linux ports that still provide gettimeofday through vDSO are not changed. Remove sysdeps/unix/clock_gettime.c, which implemented clock_gettime using gettimeofday; new OS ports must provide a real implementation of clock_gettime. Rename sysdeps/mach/gettimeofday.c to sysdeps/mach/clock_gettime.c and convert into an implementation of clock_gettime. It only supports CLOCK_REALTIME; Mach does not appear to have any support for monotonic clocks. It uses __host_get_time, which provides at best microsecond resolution. Hurd is currently using sysdeps/posix/clock_getres.c for clock_getres; its output for CLOCK_REALTIME is based on sysconf (_SC_CLK_TCK), and I do not know whether that gives the correct result. Unlike settimeofday, there are no known uses of gettimeofday's vestigial "get time zone" feature that are not bugs. (The per-process timezone support in localtime and friends is unrelated, and the programs that set the kernel's offset between the hardware clock and UTC do not need to read it back.) Therefore, this feature is dummied out. Henceforth, if gettimeofday's "struct timezone" argument is not NULL, it will write zeroes to both fields. Any program that is actually looking at this data will thus think it is running in UTC, which is probably more correct than whatever it was doing before. [__]gettimeofday no longer has any internal callers, so we can now remove its internal prototype and PLT bypass aliases. The __gettimeofday@GLIBC_2.0 export remains, in case it is used by any third-party code. It also allows to simplify the arch-specific implementation on x86 and powerpc to remove the hack to disable the internal route to non iFUNC variant for internal symbol. This patch also fixes a missing optimization on aarch64, powerpc, and x86 where the code used on static build do not use the vDSO. Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu, powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu. Co-authored-by: Zack Weinberg <zackw@panix.com> Reviewed-by: Lukasz Majewski <lukma@denx.de>
Diffstat (limited to 'NEWS')
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diff --git a/NEWS b/NEWS
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@@ -21,6 +21,19 @@ Major new features:
18661-1:2014 and TS 18661-3:2015 as amended by the resolution of
Clarification Request 13 to TS 18661-3.
+* The gettimeofday function will no longer report information about a
+ system-wide time zone, expect for aarch64, powerpc, and x86 on Linux
+ which still uses the vDSO symbol (when available).
+
+ This 4.2-BSD-era feature has been deprecated for many years, as it cannot
+ handle the full complexity of the world's timezones, but hitherto we have
+ supported it on a best-effort basis. Changes required to support 64-bit
+ time_t on 32-bit architectures have made this no longer practical.
+
+ As of this release, callers of gettimeofday with a non-null 'tzp' argument
+ will always receive a 'struct timezone' whose tz_minuteswest and
+ tz_dsttime fields are zero.
+
Deprecated and removed features, and other changes affecting compatibility:
* The totalorder and totalordermag functions, and the corresponding